Process for the preparation of a reinforced article

ABSTRACT

The invention is directed to a process for the preparation of a reinforced article which comprises the step of molding a molding composition comprising pellets into the article at an elevated temperature, wherein each of the pellets has an axial length and comprises a core and a sheath around the core, wherein the core comprises an impregnating agent and a multifilament strand comprising glass fibers each having a length substantially equal to the axial length of the pellet and substantially oriented in the axial length of the pellet, wherein the sheath comprises a thermoplastic polymer; and wherein the molding composition further comprises a filler.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/916,824, filed Mar. 4, 2016, which claims priority to InternationalApplication No. PCT/EP2014/068385, filed Aug. 29, 2014, and EuropeanApplication No. 13183139.8, filed Sep. 5, 2013, all of which are herebyincorporated by reference in their entirety.

The invention relates to a process for the preparation of a reinforcedarticle.

BACKGROUND

Introduced more than half a century ago, fiber-reinforced plastics arecomposite materials with a wide range of applications in industry, forexample in the aerospace, automotive, chipping, building andconstruction industries. A reinforced article can comprise anycombination of individual materials, for example a thermoplastic polymer(the matrix) in which fibers (reinforcing fiber) have been dispersed. Agreat diversity of organic fibers, including synthetic fibers such aspolyamide, polytetrafluoroethylene, polyesters, natural fibers such ascotton, hemp, flax, jute and inorganic fibers, such as glass fibers andcarbon fibers are often used as reinforcing fibers in compositematerials.

The reinforced plastics industry has been using glass fibers indifferent forms for reinforcing polymer matrices to produce a diversityof products. Glass fibers are generally supplied as a plurality ofcontinuous, very long filaments, and can be in the form of strands,rovings or yarns. A filament is an individual fiber of reinforcingmaterial. A strand is a plurality of bundled filaments. Yarns arecollections of filaments or strands twisted together. A roving refers toa collection of strands wound into a package.

A process for producing reinforced compositions is for example describedin WO2009/080281. In this publication a process is described forproducing a long glass fiber-reinforced thermoplastic polymercomposition, which comprises the subsequent steps of:

-   -   a. Unwinding from a package of at least one continuous glass        multifilament strand containing a sizing composition;    -   b. Applying an impregnating agent to said at least one        continuous glass multifilament strand to form an impregnated        continuous multifilament strand;    -   c. Applying a sheath of thermoplastic polymer around the        impregnated continuous multifilament strand to form a sheathed        continuous multifilament strand; and    -   d. Cutting the sheathed continuous glass multifilament strand        into pellets.

The pellets that are obtained with the above-described process comprisea multifilament glass strand that has the same length as the pellet.When these pellets are molded into an article the stiffness of thearticle is not sufficient in all cases. The stiffness of an article canbe raised by raising the amount of glass fibers in the article. However,pellets which contain a higher amount than 50 wt % of glass fiberscannot be used in injection molding processes. Moreover with increasingglass fibre content the weight of the final part will increase which isnot always desirable in particular not in the automotive industry.

The manufacture of fiber reinforced thermoplastic moulded product isknown for example from U.S. Pat. No. 6,291,064. This patent discloses afibre reinforced thermoplastic resin pellet comprising a thermoplasticresin as a matrix polymer and glass fibres as the reinforcing fibres,wherein the length of the pellet is about 2 to 12 mm, the glass fibreshaving substantially the same length as the pellet are contained in anamount of 20 to 60 vol % of the total pellet, in the state of aligned ortwisted fibres along the longitudinal direction of the pellet, and L/D²is 0.45 or more and L/D is from 1.1 to 6 wherein L represents the lengthof the pellet and D represents the diameter thereof. The pelletdisclosed in this US patent is blended with a resin pellet which doesnot substantially contain any glass fibre, and then the blend can beinjection moulded to produce the moulded product.

DETAILED DESCRIPTION

It is an object of the invention to provide a process for thepreparation of a reinforced article with an increased stiffness.

This object is achieved by the provision of a process according to theappended claims.

That is, this object is met with a process for the preparation of areinforced article which comprises the step of molding a moldingcomposition comprising pellets into the article at an elevatedtemperature, wherein each of the pellets has an axial length andcomprises a core extending along the axial length and a sheath aroundthe core, wherein the core comprises an impregnating agent and amultifilament strand comprising glass fibers each having a lengthsubstantially equal to the axial length of the pellet and substantiallyoriented in the axial length of the pellet, wherein the sheath comprisesa thermoplastic polymer, wherein the thermoplastic polymer is apropylene homopolymer or a propylene copolymer; and wherein the moldingcomposition further comprises a filler and wherein the moldedcomposition has an isotropic E-modulus of at least 5000 MPa asdetermined according to ISO527/1B at 23° C.

Preferably, the isotropic E-modulus is at least 5500 MPa, morepreferably at least 5600 MPa, for example at least 5800 or at least 6000MPa. This is surprisingly much higher than the isotropic E-modulus thatis expected when preparing an article from a glass fiber reinforcedmolding composition which does not contain a filler.

For the avoidance of doubt it should be understood that the filler is areinforcing filler, i.e. a filler that increases the stiffness (modulus)of a thermoplastic material. Non-reinforcing fillers are not to beregarded as “fillers” in the context of the present invention. A filleris considered non-reinforcing if the increase in isotropic modulus (ifany) of a composition containing 10 wt % of such filler is at most 2%,when compared to the same composition with no such fillers.

By using the process of the invention, one or more of the followingadditional advantages may also be achieved: 1) The flowability of themelted molding composition according to the invention will be improved.Because of the improved flowability the design of articles can containsmaller details (e.g. ribs) that will be filled with material duringmolding. This also allows the design of thinner articles. 2) Theshrinkage and warpage of the article prepared from the moldingcomposition according to the invention will be lower than for an articleprepared from a molding composition comprising only the glass fibers.

The pellet used in the present invention has a generally cylindricalshape having an axial length, i.e. the length in the directionperpendicular to the cross section of the cylinder. The core of thepellet has a generally cylindrical shape and comprises a multifilamentstrand made of glass fibers impregnated with an impregnating agent. Theglass fibers have a length substantially equal to the axial length ofthe pellet. The core of the pellet is surrounded around itscircumference by a sheath having a generally tubular shape comprising athermoplastic polymer.

For the avoidance of doubt it should be understood that the pellet has acore sheath structure wherein the core comprises the impregnating agentand the glass multifilament strand. The sheath consists of thethermoplastic material (optionally including the filler) and surroundsthe core. The core does not contain the material of the sheath. Suchpellet structure is obtainable by a wire-coating process such as forexample disclosed in WO 2009/080281 and is distinct from the pelletstructure that is obtained via the typical pultrusion type of processessuch as disclosed in U.S. Pat. No. 6,291,064.

The molding composition can be provided by mixing the pellets and thefiller as separate components. In this case, the pellets may be thepellets as described in WO2009/080281. Alternatively, the moldingcomposition can be provided by providing pellets comprising the filleras part of the pellets.

Accordingly, in some embodiments of the process of the invention, themolding step involves the steps of: mixing the pellets and the filler asseparate components to provide the molding composition and heating themolding composition to the elevated temperature. In this case, thefiller can be added as such to the molding composition or the filler canbe added in the form of a masterbatch comprising a polymer and a filler.This masterbatch of the filler can contain various types and amounts offiller and polymers. Mixtures of several fillers and/or polymers can bepresent in the masterbatch. The masterbatch can be provided to theprocess in the form of pellets. The polymer used in the masterbatch maybe a polypropylene, like a propylene homopolymer, a random copolymer, ora so-called heterophasic copolymer of propylene and ethylene and/oranother alpha-olefin. Most preferably, the thermoplastic polymer ispolypropylene homo- or copolymer. The thermoplastic polymer as in thesheath of the pellets and the polymer in the masterbatch are preferablyof the same type.

Mixing of the pellets and the filler can be performed in commonly usedmixing devices to provide a molding composition wherein the pellet andthe filler are homogeneously divided. Commonly used mixing devices areblenders, for example V blender, ribbon blender or a cone blender;mixers, for example a jet mixer, a planetary mixer or a Banbury mixer;or extruders. The molding composition can be heated before, duringand/or after mixing of the molding composition. The polymers in themolding composition melt and form a matrix which is to be reinforced bythe glass fibers.

Molding is performed at an elevated temperature, which is a temperatureat which the molding composition has enough flowability to be molded(i.e. the polymers in the composition are melted). The elevatedtemperature is above the melting point of the thermoplastic polymer thatis present in the sheath of the pellets. In the cases where amasterbatch comprising the filler and a polymer is used, the elevatedtemperature is also above the melting temperature of the polymer presentin the masterbatch. The elevated temperature may be suitably chosen bythe skilled person. Generally, the elevated temperature may e.g. be150-500° C., 180-400° C. or 200-300° C. In the cases where thethermoplastic polymer in the pellet is a propylene homo- or co-polymer,the elevated temperature is preferably 200-300° C.

In some embodiments of the invention, the filler is provided as a partof the pellets. Accordingly, in some embodiments of the process of theinvention, the molding step involves the step of providing the moldingcomposition comprising the pellets comprising the filler and heating themolding composition to the elevated temperature. This has the advantagethat only the pellets need to be fed to the process for the preparationof a reinforced article. Preferably, the filler is present in the sheathof the pellet.

Suitable examples of molding processes include injection molding,compression molding, extrusion and extrusion compression molding.Injection molding is widely used to produce articles such as automotiveexterior parts like bumpers, automotive interior parts like instrumentpanels, or automotive parts under the bonnet. Extrusion is widely usedto produce articles such rods, sheets and pipes. Preferably, the moldinginvolves injection molding in the process according to the invention.

With the process according to the invention reinforced articles aremade. Preferably the article is an automotive part.

Glass multifilament strands and their preparation are known in the art.The glass fibers in the strand may have been formed by any method knownto those skilled in the art. Particularly, the glass fibers may havebeen formed by a melt spinning process.

The length of the glass fibers in the strand is determined by the lengthof the pellet and may vary in a wide range. For example the averagelength may vary between 10 to 50 mm, preferably between 10-25 mm, morepreferably between 10-20 mm.

The fiber density of the fibers in the strand may vary within widelimits. Preferably, the strand may have from 500 to 10000 glassfibers/strand and more preferably from 2000 to 5000 glass fibers/strand.The diameter of the glass fibers in the strand may widely vary.Preferably, the diameter of the glass fibers in the strand ranges from 5to 50 microns, more preferably from 10 to 30 microns and most preferablyfrom 15 to 25 microns. Glass fiber diameters outside these ranges tendto result in a decrease of mechanical properties and/or enhancedabrasion of the equipment used.

The amount of the glass fibers in the multifilament strand in the pelletis preferably 5-70 wt % of based on the total weight of the moldingcomposition. The amount of the glass fibers in the multifilament strandin the pellet is preferably at least 5 wt %, preferably at least 10 wt%, more preferably at least 20 wt %. The amount of the glass in themultifilament strand in the pellet is preferably at most 70 wt %,preferably at most 60 wt % and more preferably at most 50 wt %.Preferably the amount of glass fibers (in the multifilament strand isfrom 30-50 wt % based on the weight of the molding composition and theamount of filler is from 1-20 wt % or 5-20 wt % based on the weight ofthe molding composition.

The multifilament strand may comprise a sizing composition. Suitableexamples of conventional sizing compositions include solvent-basedcompositions, such as an organic material dissolved in aqueous solutionsor dispersed in water and melt- or radiation cure-based compositions.More particularly, an aqueous sizing composition is applied on theindividual glass fibers, but also oil-based sizing compositions can beapplied.

As already described in the art, e.g. in documents EP1460166A1,EP0206189A1 or U.S. Pat. No. 4,338,233, an aqueous sizing compositiontypically includes film formers, coupling agents and other additionalcomponents. The film formers are generally present in effective amountto protect fibers from inter-filament abrasion and to provide integrityand processability for fiber strands after they are dried. Suitableexamples of film formers generally include polyurethanes, polyesters,such as polycaprolactone, polyolefins, such as polypropylene,polyamides. It is already recognized in the art that the film formershould be miscible with the polymer to be reinforced. For example,polycaprolactone may be used as film former when nylon is used aspolymer to be reinforced; for reinforcing polypropylenes, suitable filmformers generally comprise polyolefin waxes.

The coupling agents are generally used to improve the adhesion betweenthe matrix thermoplastic polymer and the fiber reinforcements. Suitableexamples of coupling agents known in the art as being used for the glassfibers include organofunctional silanes. More particularly, the couplingagent which has been added to the sizing composition is an aminosilane,such as aminomethyl-trimethoxysilane,N-(beta-aminoethyl)-gamma-aminopropyl-trimethoxysilane,gamma-aminopropyl-trimethoxysilanegamma-methylaminopropyl-trimethoxysilane,delta-aminobutyl-triethoxysilane, 1,4-aminophenyl-trimethoxysilane. In apreferred embodiment of the process of the invention, glass fibershaving a sizing composition containing an aminosilane are applied asmultifilament strands, to result in good adhesion to the matrix formedby the melted thermoplastic polymer of the sheath. Any other additionalcomponents known to the skilled person may be present in the sizingcomposition. Suitable examples include lubricants, used to preventdamage to the strands by abrasion, antistatic agents, crosslinkingagents, plasticizers, surfactants, nucleation agents, antioxidants,pigments and any combinations thereof. Applying a sizing composition tothe formed glass filaments is well-known in the art.

Typically, after applying the sizing composition on the glass fibers,the fibers are bundled into strands and then wound on bobbins to form apackage. A multifilament strand which contains at most 2 wt % of asizing composition based on the total weight of the glass fibers in themultifilament strand is preferably employed in the pellets used in theprocess of the invention. The amount of the sizing composition can bedetermined by loss on ignition (LOI). The LOI is a well-known techniquefor determining the amount of sizing on glass fibers. More preferably, amultifilament strand containing from 0.1 to 1 wt % of sizingcomposition, as determined by loss on ignition (LOI) is used.

Preferably, strand(s) comprising glass fibers on which a sizingcomposition has been applied as aqueous dispersion are employed in thepellet according to the invention.

In the process according to the invention, a pellet comprising animpregnating agent in the core is used.

The impregnating agent used in the process according to the presentinvention comprises at least one compound that is compatible with thethermoplastic polymer. The impregnating agent enables the enhanceddispersion of the fibers in the thermoplastic polymer matrix during themolding process.

The viscosity of the impregnating agent preferably is lower than 100 cS,more preferably lower than 75 cS and most preferably lower than 25 cS atapplication temperature. The viscosity of the impregnating agentpreferably is higher than 2.5 cS, more preferably higher than 5 cS, andmost preferably higher than 7 cS at the application temperature. Animpregnating agent having a viscosity higher than 100 cS is difficult toapply to the multifilament strand comprising glass fibers. Low viscosityis needed to facilitate good wetting performance of the fibers, but animpregnating agent having a viscosity lower than 2.5 cS is difficult tohandle, e.g., the amount to be applied is difficult to control; and theimpregnating agent could become volatile. Without wishing to be bound toany theory, the inventors believe that the impregnation of themultifilament strands, without separating or spreading of individualfilaments, by the impregnating agent is driven mainly by capillaryforces.

The application temperature is chosen such that the desired viscosityrange is obtained. For example, when the matrix is polypropylene, theapplication temperature of the impregnating agent can be from 15 to 200°C.

The amount of impregnating agent applied to the multifilament strandcomprising glass fibers depends on the thermoplastic matrix, on the size(diameter) of the fibers forming the strand, and on type of sizing thatis on the surface of the fibers. The pellet according to the inventionmay comprise 1-10 wt % impregnating agent based on the weight of theglass fibers in the multifilament strand in the pellet. The amount ofimpregnating agent in the pellet may be at least 1 wt %, preferably atleast 2 wt %, more preferably at least 3 wt % based on the weight of theglass fibers in the multifilament strand in the pellet. The amount ofimpregnating agent in the pellet may be at most 10 wt %, preferably atmost 9 wt % and more preferably at most 8 wt % based on the weight ofthe glass fibers in the multifilament strand in the pellet. Theimpregnating agent assists homogeneous dispersion of glass fibers in thethermoplastic polymer matrix during molding, but the amount should notbe too high, because an excess of the amount of impregnating agent mayresult in decrease of mechanical properties of the articles. It is foundthat the lower the viscosity, the less impregnating agent can beapplied. For instance, in case the thermoplastic matrix is polypropylenehomopolymer with a melt index MFI of 25 to 65 g/10 min (230 degreesC./2.16 kg) and the reinforcing glass filaments have a diameter of 19micron, the impregnating agent is preferably applied to themultifilament strand in an amount of from 2 to 10 wt %.

The amount of the impregnating agent is preferably 0.05-6 wt % based onthe total weight of the molding composition.

The impregnating agent should be compatible with the thermoplasticpolymer to be reinforced, and may even be soluble in said polymer. Theskilled man can select suitable combinations based on general knowledge,and may also find such combinations in the art. Suitable examples ofimpregnating agents include low molar mass compounds, for example lowmolar mass or oligomeric polyurethanes, polyesters such as unsaturatedpolyesters, polycaprolactones, polyethyleneterephthalate,poly(alpha-olefins), such as branched polyethylenes and polypropylenes,polyamides, such as nylons, and other hydrocarbon resins. As a generalrule, a polar thermoplastic polymer matrix requires the use of animpregnating agent containing polar functional groups; a non-polarpolymer matrix involves using an impregnating agent having non-polarcharacter, respectively. For example, for reinforcing a polyamide orpolyester, the impregnating agent may comprise low molecular weightpolyurethanes or polyesters, like a polycaprolactone. For reinforcingpolypropylenes, the impregnating agent may comprise branchedpoly(alpha-olefins), such as polyethylene waxes, modified low molecularweight polypropylenes, mineral oils, such as, paraffin or silicon andany mixtures of these compounds. Preferably, the impregnating agentcomprises a branched poly(alpha-olefin) and, more preferably, theimpregnating agent is a branched polyethylene wax. In the cases thethermoplastic polymer is polypropylene the wax is optionally mixed withfor example from 10 to 80, preferably 20-70 wt % of a hydrocarbon oil orwax, like a paraffin oil, to reach the desired viscosity level.

The impregnating agent is non-volatile, and substantially solvent-free.Being non-volatile means that the impregnating agent does not evaporateunder the application and processing conditions applied; that is it hasa boiling point or range higher than said processing temperatures. Inthe context of present application, “substantially solvent-free” meansthat impregnating agent contains less than 10 percent by mass ofsolvent, preferably less than 5 percent by mass solvent. Mostpreferably, the impregnating agent does not contain any organic solvent.

The impregnating agent may further be mixed with other additives knownin the art. Suitable examples include lubricants; antistatic agents; UVstabilizers; plasticizers; surfactants; nucleation agents; antioxidants;pigments; dyes; and adhesion promoters, such as a modified polypropylenehaving maleated reactive groups; and any combinations thereof, providedthe viscosity remains within the desired range.

In the process according to the invention a filler is used. The fillerpreferably is a particulate filler, which may be of any configuration,for example spheres, plates, fibers, acicular, flakes, whiskers, orirregular shapes. Suitable fillers typically have an average longestdimension of about 1 nanometer to about 500 micrometers, specificallyabout 10 nanometers to about 100 micrometers. The average aspect ratio(length:diameter) of some fibrous, acicular, or whisker-shaped fillers(e.g., glass or wollastonite) may be about 1.5 to about 1000, althoughlonger fibers are also within the scope of the invention. The meanaspect ratio (mean diameter of a circle of the same area:mean thickness)of plate-like fillers (e.g., mica, talc, or kaolin) may be greater thanabout 5, specifically about 10 to about 1000, more specifically about 10to about 200. Bimodal, trimodal, or higher mixtures of aspect ratios mayalso be used.

The filler with a sphere, plate, acicular, flake or irregular shapepreferably has a particle size of 0.01 to 10 μm, more preferably of 0.1to 8 μm, most preferably of 0.1 to 5 μm. The particle size is expressedas the D50 of the particles. This means that 50 weight % of theparticles has a size that falls within the above-mentioned ranges.

For fillers with a fiber or whisker shape the fiber diameter ispreferably between 1 and 20 μm, more preferably between 5 and 15 μm. Thelength of the fibers, before molding, is preferably between 1 and 10 mm,more preferably between 2 and 8 mm.

The fillers may be of natural or synthetic, mineral or non-mineralorigin, provided that the fillers have sufficient thermal resistance tomaintain their solid physical structure at least during the moldingprocess. Suitable fillers may include clays, nanoclays, carbon black,wood flour either with or without oil, various forms of silica(precipitated or hydrated, fumed or pyrogenic, vitreous, fused orcolloidal, including common sand), glass, metals, inorganic oxides (suchas oxides of the metals in Periods 2, 3, 4, 5 and 6 of Groups lb, lib,Ilia, Illb, IVa, IVb (except carbon), Va, Via, Vila and VIII of thePeriodic Table), oxides of metals (such as aluminum oxide, titaniumoxide, zirconium oxide, titanium dioxide, nanoscale titanium oxide,aluminum trihydrate, vanadium oxide, and magnesium oxide), hydroxides ofaluminum or ammonium or magnesium, carbonates of alkali and alkalineearth metals (such as calcium carbonate, barium carbonate, and magnesiumcarbonate), antimony trioxide, calcium silicate, diatomaceous earth,fuller earth, kieselguhr, mica, talc, slate flour, volcanic ash, cottonflock, asbestos, kaolin, alkali and alkaline earth metal sulfates (suchas sulfates of barium and calcium sulfate), titanium, zeolites,wollastonite, titanium boride, zinc borate, tungsten carbide, ferrites,molybdenum disulfide, asbestos, cristobalite, aluminosilicates includingVermiculite, Bentonite, montmorillonite, Na-montmorillonite,Ca-montmorillonite, hydrated sodium calcium aluminum magnesium silicatehydroxide, pyrophyllite, magnesium aluminum silicates, lithium aluminumsilicates, zirconium silicates, and combinations comprising at least oneof the foregoing fillers. Suitable fibrous fillers include glass fibers,basalt fibers, aramid fibers, carbon fibers, carbon nanofibers, carbonnanotubes, carbon buckyballs, ultrahigh molecular weight polyethylenefibers, melamine fibers, polyamide fibers, cellulose fiber, metalfibers, potassium titanate whiskers, and aluminum borate whiskers.

Of These, calcium carbonate, talc, glass fibers, carbon fibers,magnesium carbonate, mica, silicon carbide, kaolin, wollastonite,calcium sulfate, barium sulfate, titanium, silica, carbon black,ammonium hydroxide, magnesium hydroxide, aluminum hydroxide, andcombinations comprising at least one of the foregoing are preferred.More preferably, the filler is selected from talc or glass fibers (otherthan the fibers in the core of the pellets).

Optionally, the fillers may be surface modified, for example treated soas to improve the compatibility of the filler and the thermoplasticpolymer which facilitates de-agglomeration and the uniform distributionof fillers into the polymers. Surface modification of fillers is knownto the skilled person.

Talc is a relatively abundant, inexpensive, highly hydrophobic andgenerally unreactive mineral. It can be categorized as a hydratedmagnesium silicate and its main components can be represented by, interalia, one or more of the formulas (Si₂O₅)₂Mg₃(OH)₂, Si₈Mg₆O₂₀(OH)₄ orMg₁₂Si₁₆O₄₀(OH)₈. Talc suitable for use as filler is commerciallyavailable from for example Imerys or Luzenac. Talc is available indifferent colours, such as green, blue, black and white. Depending onthe application, talc with a specific colour may be used. For manyapplications however, it is desired to use a white talc.

As used in the process of the invention, ‘talc’ refers to both naturaland synthetic talc.

Talc is available in several particle sizes, for example the particlesizes of talc are classified as ‘ultrafine’ (average particle size oflower than 1 μm, for example an average particle size in the range of0.3 to 0.9 μm) and ‘fine’ (average particle size of at least 1 μm, forexample an average particle size of 1 μm to 5 μm). Preferably, fine orultrafine powder particles are used in the process of the presentinvention.

In the process according to the invention the molding compositionpreferably comprises 1-25 wt % of the filler based on the total weightof the molding composition. The amount of the filler is at least 1 wt %,preferably at least 2 wt %, more preferably at least 4 wt %. The amountof filler is at most 25 wt %, preferably at most 22 wt % and morepreferably at most 20 wt %.

In the process according to the invention pellets are used comprising asheath comprising a thermoplastic polymer.

The thermoplastic polymer in the sheath of the pellets is apolypropylene homo- or copolymer. The thermoplastic polymer may be asingle grade of polypropylene but may also be a mixture of at least twodifferent polypropylene grades.

The sheath may further contain one or more common additives, for examplestabilisers, processing aids, impact-modifiers, flame-retardants, acidscavengers, inorganic fillers, colorants, or components that furtherenhance properties of the fiber reinforced article, like compounds thatenhance interfacial bonding between polymer and glass filaments. It ispreferred that the molding composition, in particular the thermoplasticof the sheath comprises one or more of a functionalized polyolefin, likea maleated polypropylene. The amount of the functionalized polyolefinthat is added is dependent on the reinforced article and is normally 0.1to 2 wt % with respect to the weight of the glass fibers in themultifilament strand, preferably 0.2 to 1.5 wt %.

The amount of the thermoplastic polymer in the sheath of the pellets ispreferably 15-94.5 wt %, more preferably 20-90 wt %, more preferably25-80 wt %, more preferably 30-70 wt %, based on the total of themolding composition.

In the cases where the molding composition comprises a masterbatchcomprising the filler and the polymer, the sum of the amount of thepolymer in the sheath of the pellets and the polymer in the masterbatchis 15-94.5 wt %, more preferably 20-90 wt %, more preferably 25-80 wt %,more preferably 30-70 wt %, based on the total of the moldingcomposition.

The invention is also directed to a molding composition comprisingpellets, wherein each of the pellets has an axial length and comprises acore extending along the axial length and a sheath around the core,wherein the core comprises an impregnating agent and a multifilamentstrand comprising fibers each having a length substantially equal to theaxial length of the pellet and substantially oriented in the axiallength of the pellet, wherein the sheath comprises a thermoplasticpolymer; and wherein the molding composition further comprises a filler.

Preferably, the molding composition comprises 5-70 wt % of the glassfibers in the multifilament strand and 0.5-25 wt % of the filler. Morepreferably, the molding composition comprises 20-60 wt % of the glassfibers in the multifilament strand and 0.5-25 wt % of the filler.Preferably, the sum of the glass fibers in the multifilament strand, thefiller and the polymer (the thermoplastic polymer in the pellets and thepolymer in any masterbatch) is at least 90 wt %, at least 95 wt % or atleast 98 wt % of the total of the molding composition.

The molding composition can comprise the pellets and the filler asseparate components. Alternatively, the molding composition can comprisethe filler as part of the pellets. Preferably, the filler is present inthe sheath of the pellet.

Further the invention is directed to a pellet having an axial length andcomprising a core extending along the axial length and a sheath aroundthe core, wherein the core comprises an impregnating agent and amultifilament strand comprising glass fibers each having a lengthsubstantially equal to the axial length of the pellet and substantiallyoriented in the axial length of the pellet, wherein the sheath comprisesa thermoplastic polymer and a filler.

Preferably, the pellet comprises 5-70 wt % of the glass fibers in themultifilament strand and 0.5-25 wt % of the filler. More preferably, thepellet comprises 20-60 wt % of the glass fibers in the multifilamentstrand and 0.5-25 wt % of the filler. Preferably, the sum of the glassfibers in the multifilament strand, the filler and the thermoplasticpolymer in the pellets is at least 90 wt %, at least 95 wt % or at least98 wt % of the total of the molding composition.

The diameter of the multifilament strand in the pellet may e.g. bebetween 60 and 70 mm when the core of the pellet comprises one strandand between 90 and 100 mm when the core of the pellet comprises 2strands.

The thickness of the sheath of the pellet preferably is at least 0.1 mm,more preferably at least 0.2 mm, most preferably at least 0.3 mm. Thethickness of the sheath of thermoplastic polymer is preferably at most 1mm, more preferably at most 0.5 mm, most preferably at most 0.45 mm. Thethickness of the sheath is determined largely by the dimension of theglass multifilament strand and the desired amount of glass fibres in thefinal molding composition.

The length of the pellet preferably is between 10 to 50 mm, morepreferably between 10-25 mm, most preferably between 10-20 mm.

The pellet according to the invention can be prepared by a process whichcomprises the steps of:

-   -   a. applying an impregnating agent to at least one multifilament        strand comprising glass fibers to form an impregnated        multifilament strand and    -   b. applying a sheath comprising a thermoplastic polymer and a        filler around the impregnated multifilament strand to form a        sheathed multifilament strand.

Although the invention has been described in detail for purposes ofillustration, it is understood that such detail is solely for thatpurpose and variations can be made therein by those skilled in the artwithout departing from the spirit and scope of the invention as definedin the claims.

It is further noted that the invention relates to all possiblecombinations of features described herein, preferred in particular arethose combinations of features that are present in the claims.

It is also to be understood that a description on a product comprisingcertain components also discloses a product consisting of thesecomponents. Similarly, it is also to be understood that a description ona process comprising certain steps also discloses a process consistingof these steps.

The invention will now be elucidated by way of the following exampleswithout however being limited thereto.

EXAMPLES

Testing Methods

Injection molding of samples for measuring isotropic strength andisotropic

modulus was done on an Arburg 320T using a mould with dimensions

of 270×310×3 mm. The injection molding machine has 8 temperature zones(220, 220, 230, 230, 235, 235, 240, 240° C.). Injection pressure is 800bar and backpressure is 150 bar.

Specimen types as defined by ISO 527/1B were machined from platesobtained or cut by water jet, taking care to obtain smooth specimenedges.

Tensile testing was carried out according to ISO 527/1B at 23° C.

Test speed for determining E-modulus was 1 mm/min and tensile strengthand elongation at break was determined at a test speed of 5 mm/min.

At least 6 specimens per orientation (0°, 45° and 90°) were tested.

Example 1

A molding composition was prepared by mixing pellets comprising glassfibers and a masterbatch comprising talc.

The molding composition was injection molded into test samples.Isotropic E-modulus, tensile strength and elongation at break weredetermined. Results are summarized in Table I.

Pellets Comprising Glass Fibers

Pellets (glass filled pellets) were provided, comprising a core whichcomprises a multifilament strand, comprising glass fibers and animpregnating agent, and a sheath comprising a thermoplastic polymer. Thepellets had a length of 15 mm.

The multifilament strand comprising glass fibers was obtained from PPGFiber Glass; LFT9000 (fiber diameter 19 μm, 4000 fibers/strand); aminosilane sizing.

The impregnating agent used was a blend of 40 wt % Vybar 260 supplied byBaker Hughes with 30 wt % of Microsere® 5981A and 30 wt % of Microsere®5788A supplied by IGI.

The thermoplastic polymer in the sheath was SABIC® PP579S propylenehomopolymer with a MFI of 45 g/10 min (230° C./2.16 kg).

Masterbatch Comprising Filler

Pellets of a masterbatch comprising 70 wt % of a polymer and 30 wt % ofan ultrafine talc filler were provided by using a ZE40/43D extruder;side feeder: house 4; vacuum in house 9. The compounding temperature was210° C.

The polymer used to prepare the masterbatch was SABIC® PP579S propylenehomopolymer with a MFI of 45 g/10 min (230° C./2.16 kg). The ultrafinetalc was HTP ultra5c (d50=0.45 um) supplied by IMI Fabi.

The molding composition comprised comprising 64 wt % of polypropylene,30 wt % of glass fibers and 1 wt % of talc. The remaining portionconsisted of the impregnating agent and additives.

Examples 2-10

Example 1 was repeated with different compositions of pellets andmasterbatches to obtain the compositions summarized in Table 1. Resultsare summarized in Table I.

Comparative Experiment A-C

Experiment A was performed as a comparative experiment for examples 1-3.The process described under Example 1 was repeated except that nomasterbatch comprising the fillers was used. Experiment B was performedas a comparative experiment for examples 4-6. Experiment C was performedas a comparative experiment for examples 9 and 10. The compositions andthe results are summarized in Table 1.

Example 11

A molding composition comprising 45 wt % of glass fibers and 5 wt % oftalc was prepared from pellets comprising glass fibers and talc. Themolding composition was injection molded into test samples. E-modulus,tensile strength and elongation at break were determined. Results aresummarized in Table II.

Pellets Comprising Glass Fibers and Talc

Pellets comprising talc filler in the sheath of thermoplastic polymerwere prepared according to the following method.

The glass fiber multifilament strand was obtained from PPG Fiber Glass.Type: LFT9000 (fiber diameter 19 μm, 3000 tex, 4000 fibers/strand);amino silane sizing. A blend similar to the blend disclosed in WO2009/080281 being a blend of 30 mass % Vybar 260 (hyper-branchedpolymer, supplied by Baker Petro lite) and 70 mass % Paralux oil(paraffin, supplied by Chevron) was used as impregnating agent. Theimpregnating agent was melted and mixed at a temperature of 160° C. andapplied to the continuous glass multifilament strands.

The sheathing step was performed in-line directly after the impregnatingstep, using a 75 mm twin screw extruder (manufactured by Berstorff,screw UD ratio of 34), at a temperature of about 250° C., which fed ablend of the melted thermoplastic polymer and the ultrafine talc fillerto an extruder-head wire-coating die having a die-hole of 2.8 mm. Theline speed for impregnating and sheathing was 250 m/min.

The thermoplastic polymer was SABIC® PP579S propylene homopolymer with aMFI of 45 g/10 min (230° C./2.16 kg).

The ultrafine talc was HTP ultra5c (d50=0.45 um) supplied by IMI Fabi.

The sheathed strand was cut into pellets of 12 mm length that weremolded into test samples. The results are summarized in Table II.

Examples 12-15

Example 11 was repeated with different compositions of pellets to obtainthe compositions summarized in Table II. Results are summarized in TableII.

Example 16

Example 11 was repeated using pellets comprising short glass fibersinstead of talc particles.

The short glass fiber was DS 2100-13P from 3B, fibre diameter 13 μm,fiber length 3-5 mm, amino silane sizing.

Example 17-18

Example 1 was repeated using a masterbatch comprising short glass fibersinstead of talc particles.

The short glass fiber was DS 2100-13P from 3B, fibre diameter 13 μm,fiber length 3-5 mm, amino silane sizing.

TABLE I. Talc Filler in Masterbatch. Isotropic Isotropic Isotropic E-Tensile Elongation at Example or LGF Talc modulus strength breakExperiment [wt %] [wt %] [MPa] [MPa] [%] A 30 0 3938 67.2 2.6 1 30 14034 66.0 2.4 2 30 10 4656 58.4 2.3 3 30 20 5460 56.1 2.0 B 40 0 485469.1 2.2 4 40 1 5045 66.2 1.9 5 40 10 5575 59.7 1.6 6 40 20 6290 52.71.4 7 45 5 5574 60.9 1.8 8 45 15 6223 51.8 1.4 C 50 0 5769 67.0 1.7 9 501 5861 63.3 1.5 10  50 10 6284 53.7 1.4 * The Long Glass Fiber (LGF) isthe amount of glass fiber originating from the glass filled pellets.

TABLE II Talc Filler in Sheath. Exam- Isotropic Isotropic Isotropic pleor Talc E- Tensile Elongation Exper- size d50 LGF Talc modulus strengthat break iment (μm) [wt %] [wt %] [MPa] [MPa] [%] 11 0.45 45 5 5900.460.9 1.6 12 0.45 40 10 5843.2 57.5 1.6 13 0.45 30 20 5885.1 53.3 1.7 148 40 10 5801.6 56.4 1.6 15 1.5 40 10 5869.5 57.0 1.6

TABLE III Short Glass Filler in Masterbatch or Sheath. Exam- ShortIsotropic Isotropic Isotropic ple or glass E- Tensile Elongation Exper-LGF filler modulus strength at break iment [wt %] [wt %] [MPa] [MPa] [%]16 Filler in 30 20 6103.9 68.3 1.8 sheath 17 Filler in 30 20 5822.9 62.71.6 master- batch 18 Filler in 40 13.3 6120.4 63.6 1.5 master- batch

From the results it becomes clear that with both a talc filler and ashort glass filler articles can be obtained wherein the material of thearticle has a high isotropic E-modulus. Favorable tensile strength andelongation break are also obtained.

It is further shown that both a preparation process with the filler inthe sheath and a preparation process with the filler supplied as amasterbatch gives good results for obtaining a material with a highIsotropic E-modulus.

Higher isotropic E-modulus can be obtained with an increasing amount ofthe long glass fibers and the filler.

Use of short glass fibers as the filler was found to give a higherIsotropic E-modulus than use of talc particles.

The invention claimed is:
 1. A process for the preparation of areinforced article, comprising: molding a molding composition comprisingpellets into the article at an elevated temperature, wherein theelevated temperature is a temperature at which the molding compositionhas enough flowability to be molded, wherein each of the pellets has anaxial length and comprises a core extending along the axial length and asheath around the core, wherein the core comprises an impregnating agentand a multifilament strand comprising glass fibers each having a lengthsubstantially equal to the axial length of the pellet and substantiallyoriented in the axial length of the pellet, wherein an amount of theglass fibers in the multifilament strand in the pellet is at least 20 wt%; wherein the sheath comprises a thermoplastic polymer, wherein thethermoplastic polymer is a propylene homopolymer or a propylenecopolymer; and wherein the molding composition further comprises afiller and wherein the molded composition has an isotropic E-modulus ofat least 5000 MPa as determined according to ISO527/1B at 23° C.
 2. Theprocess according to claim 1, wherein the filler is present in thesheath of the pellet.
 3. The process according to claim 1, wherein thefiller comprises talc particles or glass fibers.
 4. The processaccording to claim 1, wherein the molding step involves injectionmolding.
 5. The process according to claim 1, wherein the moldingcomposition comprises 5-70 wt % of the glass fibers in the multifilamentstrand and 0.5-25 wt % of the filler based on the weight of the moldingcomposition.
 6. The process according to claim 5, wherein the moldingcomposition comprises 20-60 wt % of the glass fibers in themultifilament strand based on the weight of the molding composition. 7.The process according to claim 1, wherein the amount of glass fibers inthe multifilament strand is from 30-50 wt % based on the weight of themolding composition and the amount of filler is from 1-20 wt % based onthe weight of the molding composition.
 8. An article, obtainable by theprocess according to claim
 1. 9. The article according to claim 8,wherein the article is an automotive part.
 10. The process according toclaim 1, wherein the isotropic E-modulus is at least 6000 MPa asdetermined according to ISO527/1B at 23° C.
 11. The process according toclaim 1, wherein the viscosity of the impregnating agent is less than100 Centistokes.
 12. The process according to claim 1, wherein theimpregnating agent is present in an amount of 0.05 to 6 weight percentbased on the total weight of the molding composition.
 13. The processaccording to claim 1, wherein the elevated temperature is above themelting point of the thermoplastic polymer that is present in the sheathof the pellets.
 14. The process according to claim 1, wherein theelevated temperature is 150-500° C.